The influence of sown margin strips, management and boundary structure on herbaceous field margin vegetation in two neighbouring farms in southern England

Field margins are refugia for many species in arable landscapes, but are also affected by adjacent farming operations and by margin management. Botanical diversity in 117 hedge-bottoms on two neighbouring farms in Yatesbury, Wiltshire, UK, were studied in relation to boundary structure, hedge management practices and adjacent features on the farm to which they belong. The farms differed with regard to field margin and hedge management practices, but soil type and cropping patterns were very similar. Attention was also paid to effects of sown grass strips, coppicing and gapping-up of hedges and different approaches towards field margin management. Results indicated that there were no significant differences in woody species richness between the two farms, with hedges of similar composition. There was significantly higher herbaceous species diversity on the farm with grass strips. Multivariate analyses indicated that community differences were present, with a number of annual and biennial plant species predominating on the farm without grass margins. Principal components analysis (PCA), redundancy analysis (RDA) with forward selection and associated Monte-Carlo permutation tests, and stepwise linear regression showed the following. (1) Sown grass and/or wildflower strips adjacent to the hedge-bottom have a positive effect on species richness of the hedge-bottom vegetation. They also reduce the abundance in the hedge-bottom of Anisantha sterilis, Galium aparine, Poa trivialis and Urtica dioica, all four considered to be pernicious weed species. (2) Coppicing, in combination with gapping-up of hedges increases species richness of the hedge-bottom vegetation and has a positive effect on floral diversity in the landscape. (3) Diversity in management, boundary structure and adjacent features within one farm increases the floral diversity at the farm scale. Diversity in management, boundary structure and adjacent features between farms increases the floral diversity on a landscape scale. (C) 2001 Elsevier Science B.V. All rights reserved.